The aim of the research is to explain the molecular basis for the conservation of energy from oxidations in cardiac muscle. Mitochondria from the myocardium will be fractionated to yield the ATP-Pi exchange system involved in oxidative phosphorylation. The role of coupling factor B in the reaction will be explored. The ATP-Pi exchange system of heart mitochondria will be fractionated further, with particular reference to the hydrophobic membrane proteins, and attempts will be made to reconstitute a minimal energy transducing system. The mechanism of coupling and uncoupler action will be studied in this simplified preparation.